U.S. Pat. No. 4,104,535 discloses a hybrid electric power generating system having a pair of energy converters each operating on a closed Rankine cycle, each energy converter including a vapor generator for vaporizing a high molecular weight organic working fluid in response to heat furnished from a burner associated with the vapor generator. Each converter also includes a hermetically sealed turbo-generator responsive to varporized working fluid for generating electrical power, and a condenser responsive to exhaust vapors from the turbo-generator for converting such vapors to a condensed liquid which is returned to the vapor generator completing the working fluid cycle. A sensor, operatively associated with each converter senses the electrical output of the turbo-generator; and a control system, responsive to the sensors, controls the burners in the converters so that each converter furnishes about half the electrical load on the system in normal operation.
One of the converters operates with a working fluid having a higher boiling point than the working fluid in the other converter; and the condenser of the one converter rejects heat into the vapor generator of the other converter when the converters are in their normal mode of operation. With this arrangement, the fuel consumption of the entire system is about 60% of the fuel consumption of either of the converters when they individually operate to furnish 100% of the electrical load.
If, during the operation of the converters, a malfunction occurs in one, the sensor associated with that converter will produce a control signal to which the control of the system responds by shutting down the malfunctioning converter and increasing fuel supply to the other converter thus enabling the latter to furnish 100% of the load. The result is a highly-reliable hybrid electric power generating system which finds great application in remotely powered sites associated with pipelines or transmission line installations.